It was Easter Sunday, and Kes Smith was in the radio room when she received the call: poachers had been spotted in a remote corner of Garamba National Park in the Democratic Republic of Congo, home to the world's last remaining northern white rhinos (Ceratotherium simum cottoni).

Smith and her husband Frasier, who have worked as conservationists in the park for over 20 years, immediately leapt into a small airplane and took off.

But they were too late. Flying along a river, they soon discovered two freshly killed rhinos and 12 dead elephants. No meat had been taken, only the rhino horns and elephant tusks.

Farther north, the South African couple spotted a caravan of 25 heavily-laden pack donkeys